Compact guided diffuse optical tomography system for imaging a lesion region

Abstract

A compact diffuse optical tomography system for generating a functional image of a lesion region is provided. The system includes a source subsystem, a probe, a detection subsystem, and a computing device. The source subsystem includes laser diodes and a laser diode driver board. The probe is configured to emit the optical waves generated by the source subsystem toward the lesion region and detect optical waves reflected by the lesion region. The detection subsystem includes a miniaturized detection board and a miniaturized data acquisition board. The miniaturized detection board includes a photomultiplier tube configured to convert the optical waves detected by the probe to electrical signals. The miniaturized data acquisition board is configured to convert electrical signals outputted by the miniaturized detection board to digital signals. The computing device is configured to receive the digital signals, reconstruct the functional image, and display the functional image.

What is claimed is: 
     
       1. A compact diffuse optical tomography (DOT) system for generating a functional image of a lesion region of a subject, comprising:
 a source subsystem including:
 a plurality of laser diodes configured to generate near-infrared (NIR) optical waves; and 
 a laser diode driver board configured to drive the plurality of laser diodes; 
 
 a probe configured to emit the optical waves generated by the source subsystem toward the lesion region and configured to detect optical waves reflected by the lesion region; 
 a detection subsystem including:
 a miniaturized detection board including a photomultiplier tube (PMT), wherein the PMT has a plurality of channels and configured to convert the optical waves detected by the probe to electrical signals, and the miniaturized detection board further includes a combined board formed as one single board and including:
 a frequency mixer configured to mix the electrical signals with reference signals to derive mixed signals; 
 a second-stage amplifier configured to amplify the mixed signals to derive amplified signals; and 
 a bandpass filter configured to filter the amplified signals to derive electrical signals of a selected frequency outputted by the miniaturized detection board; and 
 
 a miniaturized data acquisition board configured to convert the electrical signals outputted by the miniaturized detection board to digital signals, and to output the digital signals from the detection subsystem; and 
 
 a computing device separate from the source subsystem, the probe, and the detection subsystem, the computing device configured to:
 receive the digital signals sent from the detection subsystem, the digital signals comprising lesion functional data from the lesion region of the subject and reference functional data from a healthy tissue region of the subject; 
 reconstruct the functional image of the lesion region based on the digital signals by:
 transforming the lesion functional data and the reference functional data to produce perturbation data; 
 generating a preliminary estimate of the functional image by applying a truncated pseudoinverse matrix of a weight matrix to the perturbation data; and 
 generating the functional image by iteratively optimizing successive estimates of the functional image regularized by the preliminary estimate of the functional image weighted by a regularization parameter; and 
 
 
 display the functional image. 
 
     
     
       2. The compact DOT system of  claim 1 , wherein the miniaturized data acquisition board includes a three-layered board having a top layer, a bottom layer, and a ground layer disposed between the top and bottom layers, and the ground layer is configured to reduce coherent interference between electrical signals carried on the top layer and electrical signals carried on the bottom layer. 
     
     
       3. The compact DOT system of  claim 2 , wherein the three-layered board is a printed circuit board and further includes grounded through-holes placed on sides of traces of the top layer and on sides of traces of the bottom layer, and the traces of the top layer and the traces of the bottom layer are configured to carry signals. 
     
     
       4. The compact DOT system of  claim 1 , wherein the second-stage amplifier has an adjustable gain and is configured to adjust the gain to control a dynamic range of the detection subsystem. 
     
     
       5. The compact DOT system of  claim 1 , further including an ultrasound imaging device configured to localize the lesion region, and the compact DOT system is configured to generate the functional image of the lesion region. 
     
     
       6. The compact DOT system of  claim 1 , wherein the miniaturized data acquisition board includes a field programmable gate array (FPGA) configured to control a gain of the PMT. 
     
     
       7. The compact DOT system of  claim 1 , wherein the miniaturized data acquisition board includes an FPGA, and the laser diode driver board further includes one or more optical switches configured to multiplex the optical waves generated by the plurality of laser diodes, and the FPGA is configured to control the one or more optical switches. 
     
     
       8. A compact diffuse optical tomography (DOT) system for generating a functional image of a lesion region of a subject, comprising:
 a source subsystem including:
 a plurality of laser diodes configured to generate near-infrared (NIR) optical waves; and 
 a laser diode driver board configured to drive the plurality of laser diodes; 
 
 a probe configured to emit the optical waves generated by the source subsystem toward the lesion region and configured to detect optical waves reflected by the lesion region; 
 a detection subsystem including:
 a miniaturized detection board including a photomultiplier tube (PMT) having a plurality of channels and configured to convert the optical waves detected by the probe to electrical signals; and 
 a miniaturized data acquisition board configured to convert electrical signals outputted by the miniaturized detection board to digital signals, and to output the digital signals from the detection subsystem; and 
 a computing device separate from the source subsystem, the probe, and the detection subsystem, the computing device configured to: 
 receive the digital signals sent from the detection subsystem, the digital signals comprising lesion functional data from the lesion region of the subject and reference functional data from a healthy tissue region of the subject; 
 reconstruct the functional image of the lesion region based on the digital signals by:
 transforming the lesion functional data and the reference functional data to produce perturbation data; 
 generating a preliminary estimate of the functional image by applying a truncated pseudoinverse matrix of a weight matrix to the perturbation data; and 
 generating the functional image by iteratively optimizing successive estimates of the functional image regularized by the preliminary estimate of the functional image weighted by a regularization parameter; and 
 
 display the functional image. 
 
 
     
     
       9. The compact DOT system of  claim 8 , wherein the probe includes a plurality of source electrodes and a plurality of detector electrodes disposed on an opposite side of the probe from the plurality of source electrodes. 
     
     
       10. The compact DOT system of  claim 9 , wherein the plurality of source electrodes are separated from the plurality of detector electrodes by a distance from approximately 3.2 cm to approximately 8.5 cm. 
     
     
       11. The compact DOT system of  claim 8 , wherein the source subsystem is configured to generate optical waves at four optical wavelengths in a range from approximately 730 nm to approximately 830 nm. 
     
     
       12. The compact DOT system of  claim 8 , wherein the computing device is configured reconstruct the functional image by:
 providing an initial estimate of the functional image through a pseudoinverse; and 
 reconstructing the functional image through optimization using the provided initial estimate. 
 
     
     
       13. The compact DOT system of  claim 12 , wherein providing an initial estimate further includes providing an initial estimate of the functional image through Moore-Penrose pseudoinverse, and reconstructing the functional image further includes reconstructing the functional image through at least one of a Conjugate Gradient optimization and a Newton optimization for inversion using the provided initial estimate. 
     
     
       14. The compact DOT system of  claim 8 , wherein the computing device is a portable computer and communicates with the detection subsystem via a universal series bus port. 
     
     
       15. The compact DOT system of  claim 8 , further including an ultrasound imaging device configured to localize the lesion region, and the compact DOT system is configured to generate the functional image of the lesion region. 
     
     
       16. A compact diffuse optical tomography (DOT) system for generating a functional image of a lesion region of a subject, comprising:
 a source subsystem including:
 a plurality of laser diodes configured to generate near-infrared (NIR) optical waves; and 
 a laser diode driver board configured to drive the plurality of laser diodes, wherein the laser diode driver board includes one or more optical switches configured to multiplex the optical waves generated by the plurality of laser diodes; 
 
 a probe configured to emit the optical waves generated by the source subsystem toward the lesion region and configured to detect optical waves reflected by the lesion region; 
 a detection subsystem including:
 a miniaturized detection board including a photomultiplier tube (PMT) having a plurality of channels and configured to convert the optical waves detected by the probe to electrical signals; and 
 a miniaturized data acquisition board configured to convert electrical signals outputted by the miniaturized detection board to digital signals, and to output the digital signals from the detection subsystem; and 
 
 a computing device separate from the source subsystem, the probe, and the detection subsystem, the computing device configured to:
 receive the digital signals sent from the detection subsystem, the digital signals comprising lesion functional data from the lesion region of the subject and reference functional data from a healthy tissue region of the subject; 
 reconstruct the functional image of the lesion region based on the digital signals by:
 transforming the lesion functional data and the reference functional data to produce perturbation data; 
 generating a preliminary estimate of the functional image by applying a truncated pseudoinverse matrix of a weight matrix to the perturbation data; and 
 generating the functional image by iteratively optimizing successive estimates of the functional image regularized by the preliminary estimate of the functional image weighted by a regularization parameter; and 
 
 display the functional image. 
 
 
     
     
       17. The compact DOT system of  claim 16 , wherein the laser diode driver board is configured to provide current to drive the plurality of laser diodes and further includes a plurality of bias-tees each configured to provide a radio frequency input to one of the plurality of laser diodes. 
     
     
       18. The compact DOT system of  claim 16 , wherein the source subsystem further includes control modules configured to control temperatures of the plurality of the laser diodes and a cooling system controlled by the control modules and configured to cool the plurality of laser diodes. 
     
     
       19. The compact DOT system of  claim 16 , further including an ultrasound imaging device configured to localize the lesion region, and the compact DOT system is configured to generate the functional image of the lesion region. 
     
     
       20. The compact DOT system of  claim 16 , wherein the miniaturized data acquisition board includes a field programmable gate array configured to control the one or more optical switches.